A next-generation multimedia wireless communication system, on which research has been actively carried out in recent years, requires various kinds of information, such as images and wireless data, to be processed at higher data transmission rate in addition to initial sound-based services.
In recent years, Orthogonal Frequency Division Multiplexing (OFDM) having a high data transmission rate has attracted considerable attention. OFDM is a multiple carrier modulation method that is capable of dividing a frequency band into a plurality of orthogonal subcarriers to transmit data, thereby reducing inter-symbol interference at low complexity.
It is necessary for orthogonality of a subcarrier to be maintained in a frequency level. Each orthogonal channel goes through mutually independent frequency selective fading and intervals between transmitted symbols are increased, thereby minimizing inter-symbol interference. Orthogonal Frequency Division Multiple Access (OFDMA) is a method of independently providing a portion of usable subcarriers to each user to realize multiple access in a system using OFDM as a modulation method. OFDMA provides frequency resources, such as subcarriers, to each user. The frequency resources may be independently provided to a plurality of users; therefore, the frequency resources may generally overlap each other. As a result, the frequency resources may be exclusively allocated per user. In an OFDMA system, frequency diversity for multiple users may be acquired through frequency selective scheduling and subcarriers may be allocated in various ways using a permutation method for the subcarriers.
In a few wireless communication systems, when a mobile station transmits an uplink signal to a base station, an uplink control channel to transmit a control signal and an uplink data channel to transmit data may be physically divided. In addition, a plurality of control/data channels may be simultaneously transmitted using one symbol. Transmit power of each uplink transmission channel may be determined through a specific equation.
The base station may receive a power status report (PSR) from the mobile station to perform the next scheduling of the mobile station. The recent wireless communication system adopts a carrier aggregation (multiple carriers) method and a fractional frequency reuse (FFR) method to improve communication performance. So far, however, a PSR reporting mode in the multiple carrier system and the system adopting the FFR method and a problem of exceeding the maximum power limit which may be generated during multiple transmission have not been concretely proposed.